Laser-ultrasound-based non-destructive testing—optimization of the thermoelastic source

Faëse, Frédéric; Jenot, Frédéric; Ouaftouh, Mohammadi; Duquennoy, Marc; Ourak, Mohamed

doi:10.1088/0957-0233/26/8/085205

Cited by 9 publications

(6 citation statements)

References 15 publications

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“…In this landscape, optical techniques appear to be conceivably the most promising ones because of their versatility, good sensitivity and resolution, the wide frequency band of the signal they can generate and receive, and their applicability to almost all types of material. The excitation of ultrasound is quite easy to obtain with pulsed lasers 11 – 14 or continuous modulated lasers 15 , 16 , using the photoacoustic effect in elastic or ablation regime (plasma-generated ultrasound), applicable practically both on any material of engineering interest and on various types of surfaces, being rough, smooth, reflective or opaque.…”

Section: Introductionmentioning

confidence: 99%

Non-contact ultrasonic inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

Gulino

Bruzzi

Caron

et al. 2022

Sci Rep

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Gas-Coupled Laser Acoustic Detection (GCLAD) is an ultrasonic, non-contact detection technique that has been recently proven to be applicable to the inspection of mechanical components. GCLAD response raises as the intersection length between the probe laser beam and the acoustic wavefront propagating in the air increases; such feature differentiates the GCLAD device from other optical detection instruments, making it a line detection system rather than a point detector. During the inspection of structures mainly extending in two dimensions, the capability to evidence presence of defects in whichever point over a line would enable moving the emitter and the detector along a single direction: this translates in the possibility to decrease the overall required time for interrogation of components compared to point detectors, as well as generating simpler automated monitoring layouts. Based on this assumption, the present study highlights the possibility of employing the GCLAD device as a line inspection tool. To this end, preliminary concepts are provided allowing maximization of the GCLAD response for the non-destructive testing of components which predominantly extend in two dimensions. Afterwards, the GCLAD device is employed in pulse-echo mode for the detection of artificial defects machined on a 12 mm-thick steel plate: the GCLAD probe laser beam is inclined to be perpendicular to the propagation direction of the airborne ultrasound, generated by surface acoustic waves (SAWs) in the solid which are first reflected by the defect flanks and subsequently refracted in the air. Numerical results are provided highlighting the SAW reflection patterns, originated by 3 mm deep surface and subsurface defects, that the GCLAD should interpret. The subsequent experimental campaign highlights that the GCLAD device can identify echoes associated with surface and subsurface defects, located in eight different positions on the plate. B-scan of the component ultimately demonstrates the GCLAD performance in accomplishing the inspection task.

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Section: Introductionmentioning

confidence: 99%

Non-contact ultrasonic inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

Gulino

Bruzzi

Caron

et al. 2022

Sci Rep

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“…Rayleigh wave is dispersive while propagating in a structure composed of a film on a substrate, due to its interaction with two layers at the same time. Indeed, it is sensitively related to the thickness of the layer and its adhesion to the substrate [2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Characterization of Adhesion by Rayleigh Modes Generated and Detected by Lasers

Baher,

Chrifi Alaoui,

Jenot

et al. 2022

Proceedings of the 10th Convention of the European Acoustics Association Forum Acusticum 2023

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Adhesion is the ability of dissimilar particles to clutch together and is used to describe the contact between two interfaces. It is often considered as the predominant factor for coating reliability in thin-film technologies. Many techniques have been established to estimate the coating-substrate adhesion intensity. In this work, laserultrasonics, as a non-destructive non-contact method, is implemented to identify the adhesion level on a structure composed of a polyvinyl chloride film in contact with an aluminum sample. For the generation of elastic waves, a doubled frequency Nd:YAG laser is used. Then, the normal displacement at the surface of the substrate is detected thanks to a heterodyne interferometer of Mach-Zehnder type. Rayleigh modes dispersion curves obtained experimentally are compared to the theoretical ones, which are analytically obtained in order to evaluate the adhesion level as an inverse problem. Moreover, the finite element method is exploited to model the propagation of the surface acoustic waves on the studied sample. Indeed, it is necessary to predict the phenomena that could happen while characterizing a layer on a substrate structure. Finally, this allows to analyze the matching between experimental and numerical results while applying different degrees of adhesion.

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“…Among the ultrasonic induction methods, the photoacoustic effect obtained by pulsed lasers is undoubtedly the most efficient. Pulses of coherent radiation reach the surface of the component, triggering states of deformation by expansion (heating) and contraction (cooling) which propagate inside the material [22][23][24][25][26]. Although wave induction by pulsed lasers applies to any type of material and involves high ultrasonic amplitudes, the levels of irradiance reached often exceed 1 MW cm −2 ; hence particular care must be taken to avoid localized ablation of the component [27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Crack detection with gas-coupled laser acoustic detection technique

Vangi

Bruzzi

Caron

et al. 2021

Meas. Sci. Technol.

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Gas-coupled laser acoustic detection (GCLAD) is an unestablished ultrasonic detection technique based on the displacement that a laser beam sustains when intersected by an acoustic wave travelling in a fluid. In the present work, GCLAD for the noncontact detection of ultrasound is applied to identify surface defects on metal plates. Two GCLAD configurations are analysed, each associated with different sensitivities to cracks; specifically, GCLAD exhibits the highest sensitivity when inclined perpendicularly to the ultrasonic propagation direction in the air. The high angular selectivity allows evidencing only specific waves, those directly travelling in the component or reflected by defects. A higher ultrasonic amplitude is highlighted for GCLAD compared to air-coupled probes. The work ultimately demonstrates GCLAD's major advantage: the possibility of instantly performing an inspection over an entire line, rather than on a point as for traditional transducers.

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Laser-ultrasound-based non-destructive testing—optimization of the thermoelastic source

Cited by 9 publications

References 15 publications

Non-contact ultrasonic inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

Non-contact ultrasonic inspection by Gas-Coupled Laser Acoustic Detection (GCLAD)

Characterization of Adhesion by Rayleigh Modes Generated and Detected by Lasers

Crack detection with gas-coupled laser acoustic detection technique

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